Phase reversal telegraph system



May 24, 1949. R. P. LEROY PHASE REVERSAL TELEGRAPH SYSTEM Filed NOV. 6, 1945 INVENTOR. Rober? Pien@ Leroy ATTORNEY MOMQJ 3U DE mm.. h@

. .00E ANN w dem@ u m ZGEuim Patented May 24, 1949 PHASE REVERSAL TELEGRAPH SYSTEM Robert Pierre Leroy, Paris, France Application November 6, 1945, Serial No. 627,026

in France March 12, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 12, 1963 l, l Claim. l

The present invention relates to systems of telegraph transmission using double current, employing a code with two signal elements, ci which the first is constituted by a transmission at audio frequency, and the second is constituted by the same transmission dephased by 180 degrees.

In such a system of telegraph transmission, the sending station comprises a modulator to the control terminals of which the telegraph code transmitter applies a control current which is at certain instants a rest current of one polarity, and at other times is a marking or operating or work current of opposite polarity. The inversion in polarity of this control current has for its effect to invert the phase of the telegraph current sent in the line, every change of polarity of the control current causing an inversion of phase of the telegraph line current.

To each character transmitted, there corresponds therefore the application to the control terminals of the modulator of a succession of pulses of current which arealternately Work currents and rest currents, according to a determined code, and hence corresponds to the sending on the line of a succession oi currents of phases which are alternately inverted. For eX- ample, in the International Start-Stop Code, to the letter S there corresponds, after the sending of a work or marking current pulse corresponding to the start, the transmission, during an elementary interval, of a rest current, then during the following interval, of a work current. then during a following interval of a rest current, then during two following successive intervals of a work current, and, thereafter, :finally of a rest current corresponding to stop To each one of these inversions there corresponds a change of the phase of the current which was sent on the line, there being ve changes of phase in the course of the transmission of the letter S.

At the receiving station, there is applied to a demodulator, on the one hand, the received current including the inversions of phase, and on the other hand the reestablished carrier frequency current as it was set up in the line at the beginning of the transmission, keeping for it an unvarying phase. Thus, the current delivered at the output terminals of the receiving demodulator will change in sense or direction at the same time as the telegraph current will change its phase.

Hence, it can be said that every change of sense or direction of the current taken ofi at the output terminals of the demodulator of the receiving station corresponds to a change of sense or direction of the current applied to the control terminals of the demodulator of the transmitting station. But, on rst consideration, it cannot be known whether to a given received pulse of rest current, there corresponds, at the transmitting station, a pulse of rest current or a pulse of work current.

In order toY assure agreement between the senses or directions of the current of reception and those of transmission, it is arranged so that the first current pulse delivered at the output of the demodulator of the receiving station can only be of one determined sense or direction, and the transmission will always be commenced by the transmission of a current of this same determined sense, for example, a rest current impulse if it has been arranged that the demodulator of the receiving station shall on its first pulse deliver a rest current.

If, however, there is produced on the line an accidental transient interruption, so that the carrier current disappears for an instant, it is not known, when the continuity of the circuit is reestablished, whether the transmitting station is sending at this moment a rest signal element or a work signal element. Hence, there is the risk, following such an interruption, of receiving signals which are inverted.

In order to avoid this disadvantage, it is necessary in the case of the interruption of the circuit between the stations, to cause to come into operation a safety device disconnecting the terminal telegraph apparatus, putting at each station the transmitting modulator in the condition corresponding to the sending of a rest signal, and not putting the connection into service, after the reestablishment of the continuity of the circuit between the stations, until after determination of the fact that the received currents have againrassumed their normal values and senses.

The present invention has for an object to provide devices permitting to assure the automatic performance` of these operations, and is applicable to the case in which for the purposek of saving material, there is used at a station B, for the transmission from station B toward a station A, the carrier frequency reconstituted from the signals received from the station A. It is then possible to compare at the station A, the phase of the waves of the local generator at station A to that of the reconstituted carrier wave as re-sent by station B. The resultant variation prises a generator 3 of audio-frequency current.

whose oscillations are modulated in the sending modulator 4 by the current coming from the sender of the local telegraph sending and receiving apparatus 9, the output current of the modulator 4 at station A is sent; toward the station.

B over the line A-B, through a line filter Ma At station B, the received current passes through the line lter 1I, from there, it. passes.

to the principal demodulator 6l through two paths, of which one comprises a first amplifier 6U, and the other comprises an auxiliary demodulator T2, a. narrow band filter 65; which thus has a relatively highA time` constant, and a second! amplier 64.

Itis known thatwith such a circuit arrangement, there is deliveredf at. the. output of the second amplifier- 6,4, the-V reconstituted. carrier frequency, and, hence attl'ieoutput of the principal modulator Bgl, the: reconstitutedtelegraph signal current, if auxiliary.- demodulator 'i'Zf is controlled, by a. derivedlportion of the carrier current asreconsttuted, aataiienmi; at-,the out.- put, ofprincipal dernodulator: 61|..

The initiation. of-` the current. pulse and the orientation of, phase at. the start` are obtained bythe means-ofn a derivedportion taken off at theA input, of, rst amplifier. 6,01,A and supplying second` ampliier 6,4. through the means of a blocker 6 3, which offers. opposition tothe passage of..k the1 current Aunder nQrmal operating. conditions, undervv the effect of a? control current obtained by rectifying; thereconst'ituted carrier current bymeans of; rectifier 62; The telegraph currentv thus reconstituteda at tl'ie.- output of the Drnpal mQdlllator. 6l. issen-t to: the; telegraph receiver unit of the ordinary. terminal telegraph sending and receivingv apparatus 5,9;A at station B.

On the' other. hand, for the transmission from station B towardistationlA., a. portion ofA the-reconstituted carrierfrequency. taken, oi. at the output of second amplifier 64, iaappliedl to the sending modulator 5,4; controlled by. thei current ofthe telegraphy sender.. unit. of` the usual terminall telegraph sendingi and', receiving. apparatus 59C at At station A the; receiving; apparatusu proper is identical to that. oi-L StationfB.-

'Ihereconstitutedv carrier` wave atthe output of secondampl-ifier l4,-,at station.Ahas a denitely. determined outeof-phase rel-ation with reference tothe carrier wave; produced; by. the generator 3f attstationiu This5dephasing, relation. hasl assumed,` a value.: whichy is dennitely determined when the system starts into` operation, at the moment when; the; sending,- modulators 4 and 54 being,y both` inthe .,rest position, there is produced anA initiationf. oi;A the reconstituted carrier oscillation; The station; A comprises means,`- to give: warning! oil an: accidental variation;L from thisdeterminedl Value of dephasing. In:` the assembly shown in` the drawing, these means at station A@ comprise a; phase adjuster f. of; determinedlcharacteristicf for adjusting the phase by,` a'. fixed amount; cmpensating.. for. a certain; value` oi:` dephasing,-A aridz a. phase differ.- ence. responsive,- demodulatorf 4 65 supplied on,l the one hand by the reconstituted carrier current at the output of second amplifier I4 at station A, and, on the other hand, by the current at the output oi the phase adjuster 5. Hence, there will be at the output of phase difference responsive;v demodulator 6, a. rectiedcurrent. J whose pulsations cari be reduced. by a low-pass lter 1.

It is the Variations of this rectied current J which are used for the putting into action of the phase correcting system, because if the phase of thev receivedA signal element pulse is incorrect, the value of. this current will be altered.

In order to understand the operation of the system, it will be` assumed at first that an ac- I cidei'ital interruption takes place in the current in the direction BA, in the line BA, The rectified.` current J will decrease progressively. If the interruption is transient, the carrier wave will be"y rapidly re-established either with the correct phase if the modulator 54 which has not received asignal informing, ofA the interruption, is determining a non-operative or spacing condition at the instant of the, ria-establishment, or with the opposite phase it the modulator is, determining an operative or marking conditionat that irrstant. In the rst case, the rectified. current J will return to its; initia1=.value, in the.- second case the value. of the rectied cur-rent J- will be inverted.

Two relays I'I andl L20 are energized by the rectified current J the,- one relay H 0: responding to the inversion. and. thev other relay t28 responding to the interruptioni Relay lli!- is polarized and-,in normal operationhas.- its contact lily open, when the energizing; current changes direction it. closesl this contact. The Contact of: relay |201 is open when. its Winding is energized.

The operation; of these relays H01 and- |20 may be delayedfin order. to avoid'all-unnecessary operation` of. the device for re-establishing the correct phase. The,- putting; into.y operation of theserelays Htl-and: IZllfcreates bymeans of appropriate: contacts, compensating; currents, delaying their return4 to! non-operated condition until the, rectifiedl currentJ has returned to its initial.y value.

Armatures. H l and* l-2-.h of relays H0.- and |20 respectively: put. into: circuit in parallel the current. interruption protecting-device -or phase .correcting device'cf theistation Ai which is shown connected for actuation. byV these armatures through relay IN.-

The` functions,` of; this: interruptionprotective device: at4 station: A; areithe' following:

1. Itwill -causefthe -cpeningoi the local circuits to sender-receiver 9 at station A, until. thev re establishmentI on the-,correctiphase. It-Jwill then putthe` output .modulator f4 f at; station-Minto vnonoperativel conditiom. the modulatorsl employed beingrassumedtoihavef'a definitefoperating characteristic in the absence of control currentthat is, ,one similar; to; that; which wouldi obtain with current in; amori-operative: condition;A The; operation of the: receiving: circuit willv` bring.V about the resumption: of "the-s nonoperated i condition.

2; It will transmit; inf, a` regular: rhythmg. by means oiga-Vibratingrrelay, for exampleover the line ffrorni statioIr..A.,tostatioriiB, trains:v ofi waves whichl will: have: the: phase:-` whichi is required: to be reeestablished', because'. the: modulators'.- have been put into, non-.operative condition. These trains of waves will have a durationiTi-and will be separatedqbyianinteizval of: duration Tal. The

first interruptionsin. the. train of waves-will bring..

into operation the protecting device of station B shown in the drawing in the lower part of station B. The function of this device will be first to open the local telegraph circuits of sender-receiver 59 at station B and so bring to -the non-operative condition the output modulator 54 at station B, and arrangements will be provided to be sure that it remains so until normal conditions are completely restored, unless the successive trains of Waves alter the situation. The protective device of station B ought, therefore, to remain blocked until the reception at station B of a train of waves of longer duration than that sent during the period of re-establishment. On the other hand, the protective device 'of station A will assume the non-operated position when the termination of the interruption has allowed the rectified current J from phase difference responsive demodulator 9 to return to itsfnormal value. ment can take account of the fact that this rectified current J is higher during the period o reestablishment by reason of the disconnecting of the circuit `of the receiver at the station.

If, however, the interruption is 4produced in the direction A-B on the line A-B, it will be necessary thatthis interruption should produce the sa-me effects at station B as those which have been described above at station A. In this case, as in the preceding case, the function of the protecting device of station B will consist of cutting off the local telegraph circuits from transmitterreceiver 99 as soon as an interruption in the direc- .tion A-B will have been registered, and to put the modulator 54 in the non-operative condition before an inversion of the carrier Wave can result.

Since, at station B, no local generator of alternating current is provided, of which the phase can be compared with that of the reconstituted carrier wave, it is necessary to nd a different criterion from that used at station A to show the interruption.

A preventive measure is also required in this case, by means of which the station A may ascertain whether inversion has been produced or not.

The criterion used which will effect the operation or the protective or phase correcting device of station B, is the reduction of the amplitude of the reconstituted telegraph signals. To understand this operation, it is necessary to notice that if the carrier Wave has disappeared for a certain considerable interval of time, or if it has momentarily disappeared and reappears immediately afterwards with inversion of ite transitory phenomenon has necessarily taken place in the reconstituted telegraph signal, the duration of which phenomenon is substantially equal to that of the elementary signal element or pulse. If, at the output demodulator 6| at station B, a circuit is arranged in parallel with the circuit carrying telegraph current to Ithe usual receiver and including a rectier 16 and a low-pass filter 'I5 whose Itime constant is less than the time constant of the telegraph filters but is more than one-half of the latter, in order to avoid the action of the variations which bring about the succession of signals, a circuit will be provided adapted to energize a relay whose contacts are open in normal position when fully energized, which will have come to the non-operated or closed position when the current which it receives, which is normally substantially constant owing to the automatic gain control associated with the amplifiers, ceases or is sufficiently reduced. Relay |30 may have a denite spring bias. The exact value of The compensation or adjustcurrent'requiredforthe release of relay |30 int non-operated position can be regulated by a compensating current.

The armature |3| of relay |30 at station B, when so deenergized, will close the energizing circuit of relay |49, which will then be energized independently of contact |3| through contact |4| and through a contact |6| which remains closed until the end of the operation. Relay |40 will, at the same time, close through contact |42 the circuit of relay |50 of which the contacts |5| and |52 open the local circuits to lthe local transmitterreceiver 59, a fifth contact |55 closing a branch circuit comprising relay |60 and condenser 69 which, in turn, short-circuits the armature |32 of relay |39 in the absence of telegraph current, as well as the resistances 10 and 9|.

If current is again applied to the telegraph circuit, the contact |32 removes the short-circuit of condenser 99 which will charge slowly so that relay |09 can operate only after a certain interval of delay T3 which is greater the duration T1 of the trains of waves sent from station A. When, upon the disappearance of this current, the contact |32 short-circuits the condenser 99, and also during the whole duration of the attempts at rie-establishment of the previous condition, the armature itil of relay |60 closes a contact in series with contact 4L The device will be able to return to the non-operated -condition only when at the moment of re-establishment, a current of greater duration will have been able to manifest itself.

In order to be sure that an accidental re-establishment of the circuit does not interfere with the ree-establishing operations, the delay interval Ta should be greater than the time which separates the ascertainment of a break and that of the first interruption caused by station A.

The operation of the interruption protecting unit at station A is as follows. Relay i710 is connected in circuit and energized through contacts and |2I, and the relay V10, when energized, closes at contact the energizing circuit of relay Whose contacts |8|, |82, |83, |84, open the local circuits to local transmitter-receiver 9, and at contact |12 closes the energizing circuits of relays and |00 which are arranged to operate as an inverter.

The contacts |92, |93 of relay 90 open the connection from the generator 3 to the circuit of line A-B when relay |90 is in the energized condition. If relay |79 returns to its non-energized condition, which will evidently be when relay |90 is in the non-energized condition, the contact |72 is opened and opens the energizing circuit of the inverter unit including relays |90 and |00, the contact |9| remains closed, and, at the same time, the contacts il, |82, |83, |84, close the local circuits to local transmitter-receiver 9. In order to prevent the correcting devices from operating again under the effect of a subsequent interruption which may not have been registered yet, on account of the transmission time, 2To corresponding to the time required to traverse the double going and coming path from A to B and then from B to A, it is sufcient to arrange in parallel with contacts and 2|, a contact |9| controlled by the rela57 |90 which closes a circuit to energize relay |10 when relay |90 is in the operated condition. The disconnection of the generator can, therefore, only be effected at a definite instant by a control signal transmission traversing the entire circuit and whose reception has already commenced, which is possible if the time intervals T1 and T2 are greater than 2To. Hence, no failure of current can occur.

The operation of the inverter group including relays i90 and i'iii is las follows: Starting with .the non-operated condition, the relay 19o being traversed by no energizing current and being then in the non-operated condition, the winding of. relay tilt is then dfi-energized because its Winding is short-circuited by closed Contact |94; which also short-circuits the condenser Then, upon the closing of contact |12, the winding of relay i530 is energized and relay i90 assumas the energized. condition, but relay lill!v remains in de-energized condition. When relay i90 assumes the energized condition, its contacts |922, 1&3, open 'the connecting circuit from generator 3 to line A-B. At the same time that contact i94- opens when relay i90 becomes energized, the snort .circuit on condenser i9 is removed and condenser iS starts to charge. relay iii then starts to become energized. When relay itil becomes energized, its contact IUI is closed and short-circuits. condenser I8 andthe windincr of relay i90, which causes relay i90 to assume the de--energized condition. This will close contacts |92, |93, again completing the circuit connecting generator 3 to the line A-B. When relay iii thus assumes the ole-energized condition,y through contact 194', it again short-'circuits condenser i9 andthe winding of relay |00, and the cycle is repeated. The time periods of opera-l tion are determined by the magnitudes of the several condensers and resistances involved.

It will be apparent to those skilled in the art that my invention is susceptible of modications to adapt the same to particular conditions, and all such modiiications which are Within the scope of the appended claim I consider to be comprehended within the spirit of my invention.

I claim:

In a system of carrier frequency telegrapliy transmitting on the line signals comprising carrier frequency, signal elements `of opposite phase, a first station, a second station, two uni-directional lines connecting said stations', said first station comprising an audio carrier freH quency generator, each of said stations comprising transmitting keying means, transmitting modulating means controlled by said keying means adapted to change keying impulses of opposirte polarity into carrier frequency pulses of opposite phases, and receiving demo'dulating means adapted to change received carrier frequency pulses of opposite phases into continuous current impulses of opposite polarity, each said receiving demodulating means comprising means for deriving a portion of the received modified The winding of CTI carrier frequency current and converting the same into unmodified original carrier frequency current, said transmitting modulating means at said rst station being connected to said generator, said transmitting means at said second station. lbeing connected for ene'rgization by the carrier frequency out-put of said deriving and com verting means at said second station for convert.- ing into unmodified carrier frequency current, each of said lines connecting said transmitting modulating means of one said station to said receiving demodulating means of the Iother said station, a phase adjuster at said first station havir`1g i-'ts input connected to said generator, phase diierence responsive demodulating means at said rst station having one input connected to the output of said phase adjuster land having its other input connected to the output of said deriving and converting means `at said first station for converting into unmodified carrier fre quency current, and being adapted to deliver output direct current which is a function of the difference or phase of its two in-puts, telegraph receiving means at each said station connected to the output of said receiving dernodulating means at said station, control relay means at said rst station connected for actuation by the ouput of said phase -diiierence responsive means, pulsing relay means at said rst station having a controlled contact connected in series in the output line of said transmitting demodulating means at said first station, first interlocking reh lay means connected for actuation by said control relay means and adapted when actuated to open the circuits of said transmitting keying means to said modulating means and -of said telegraph receiving means at said rst station and also to actuate said pulsing relay means, master relay means at said second statiorna rectier and a lowpass filter at said second station connected between the output of said receiving demodulator at said second station and the actuating winding of said master relay means, and second interlocking relay means connected for actuation .by said master relay means when in deenergized condition and adapted to open the circuits of said transmitting keying means and said telegraph receiving means .at said second station, whereby a momentary opening andv immediately subsequent reel-using of either of said lines maintains the original correspondence of polarity of keyed signals from a keying means at one said station and the telegraph receiving means at the other said station.

ROBERT PIERRE LEROY.

No references cited. 

